The effect of different combinations of thinners and surfactants on the apple fruit thinning

The effect of two apple fruit thinners, metamitron (MM) and 6-benzyladenine (BA), used alone or with the addition of different surfactants, was examined on the ‘Golden Delicious’ apple cultivar in 2022. The surfactants Surfare, Trend, mineral oil (concentration 0.1%), and Inex (concentration 0.05%) in combination with MM 300 mg L^‑1 or BA 200 mg L^‑1 were applied at 13.7 mm fruit diameter.
Untreated trees (UTC) served as a control treatment.
At harvest, the fruits were divided into four classes according to their size: <60, 60-70, 70-80, and >80 mm, and for each class, the total number of fruits and yield per tree were determined.
Fruit weight, number of seeds per fruit, fruit firmness, starch-iodine index, soluble solids and total acid contents, and return bloom were also evaluated.
The combination of mineral oil with BA had the highest number of fruits per tree, significantly more than UTC, with the lowest yield of fruits larger than 70 mm in diameter.
In contrast, the combination with MM had the best thinning effect, the lowest number of fruits per tree, with the greatest reduction in the proportion of the smallest fruits (<70 mm), and the best return bloom.
The MM + Trend treatment also increased the proportion of the largest fruits in the yield.
In combination with BA, the surfactant Surfare was the most effective, resulting in a significant improvement in the return bloom compared with UTC, whereas the other surfactants had little effect or were even worse than BA alone.
The treatments did not differ in fruit-ripening parameters, except for soluble solids content.

EHC2024: International Symposium on Fruit Production Systems for Sustainable and Resilient Development

S. Spasojevic, L.J. Milosevic, J. Milivojevic, Č. Oparnica, D. Radivojević

apple thinning, surfactants, metamitron, 6-benzyladenine

https://doi.org/10.17660/ActaHortic.2026.1457.42